Fuse



Oct. 17, 1933. Q HART 1,930,804

FUSE

Filed March 16, 1932 Patented Oct. 1,7, 1933 PATENT', v

y v1,930,804 p,

rief-ieriN Y FUSE .Lester C. Hart, ,'Cleveland, Ohio, assigner torV iii-Voltage Equipment Company, a corporation of Ohiol fr Applicationlvarch 16, 1962. Serial-Nof599ii2 7 claims. (C1. 20a- 127) The invention relates 'to use equipment .for4

use in high .voltage work.` The primary object of the invention is to prevent deterioration of the fuse link or element due to corona discharge. On the higher voltages, especially 22,000 volts or higher, 'there isa corona discharge from the small diameter conductors. There is, however, a wire diameter for `each voltageat which corona discharge doesnot occur, and without such discharge, there willV be no deterioration due to the ionization or breaking down of the air surrounding the conductor. One of the objects of the invention is to provide va` fuse link which will take advantage of thisprinciple and thus avoid he disadvantages incident to coronadischarge.

Another difliculty incidentv to corona discharge, arises at the end of the fuse tube where the linkleaves the bore of the tube. When a high voltage is applied, that is about 70,000 volts,to av iuse tube, such as that shown in the drawing, a discharge is noticeable from the ljuse link to the fuse tube. discharge, brightest right at thelink, and radiating along the end of the tube. Thisis apparently a charging current which is necessary to holdthe outer end surface of the tube at line potential. This causes ionizing of the air, and

disintegration of the link where it leaves Vthe tube. Anobject of the present invention is to' ings, wherein:

Figure 1 is an assembly View.` Fig. 2 is a side elevation of the fuse llink. Fig. 3 is a section through the link on a greatly enlarged scale to more clearlyillustrate the different layers of material entering into the link. And Figs. 4, 5 and 6 are enlarged detail views of the spring clip.

Referring first to the general arrangement which shows the invention as applied to the construction of my Patent No. 1,605,543 of November 2, 1926, 1 is a fuse tube of insulating material supported at one end on the terminal member 2, and having its other end spaced above the other terminal member 3; 4 is the -fuse link` which constitutes one feature ofthe invention;

and 5 is the spring clip which constitutes a Vsecond feature of my invention. 50

. by the insulating layer 7, which in turn is surrounded for a part of its length by the metal Thismay be described as aradical spring 16.

sheath 8. 1 The wire 6 terminates at its left hand end in the copper loop 9, and -atits right hand end is coiled around the insulation, as indicated at 10. The sheath 8 is preferably oi metal foil which makes `contact at its left end with the 60- loop 9. At the other end ci the link, the sheath` terminates several inches short of the end of the insulation 7.

` The objectoi this construction is to provide l a metallic shield around the fuse link which will be'charged at line potential, but which will not carry anyfcurrent. This metallic shield is of the proper diameter for they voltage on which it is used, and as a result, there is no corona dischargeand no deterioration. Thev shield is 76 charged' irom'the terminal in the closed end of the fusevtube l and ends close Ito the outside terminal 3;

The spring clip `5 is carried by the end of the tube, and makes contact with the metallic 7X5' A shield 8 of .the fuse link. The clip brings the corona shieldl of the link in positive contact with the fuse tube end. vBeing in positive contact,A there will be `no discharge,. as the discharging current will be carried 'through the metal path, 865- thus eliminating the corona discharge which otherwiseionizes the airand causes disintegrav tion of the link where it leaves the tube.v

The spring clip is always used with the corona shield links, but is not limited to such use, as it 8553 may be used to advantage with plain metallic links. The spring pressure is relatively light and the clip `is so formed that when the fuse blows, the link is blown free of the clip.

The precise construction of the clipA will be g seen by reference tov Figs.y4, 5 and 6. It is in the form of a split bronze ring 11 clampedover the kend of the tube by the bolt 12, the lugs 13 overlying the end of the tube, and assisting in holding it in position. The ring has a projecting arm 14 953 and in opposition to this, is clamped to the strip 15 of spring material backed up by an auxiliary The boltvl'l secures the members 15 and 16 inposition, thefuse link 4 lying between 14 and 15, as indicated in Fig.` 5. A yielding 155 flexible link comprising a wire of fusible metal '165 coated with ya layer of insulating material, and

.a thin exible metallic shield surrounding said insulation and stopping short o1?` one end of the link, `said lshield being in'V electrical connection with the fuse wire. at its other end.

2. In combination in a fuse construction a iiexible link comprising a wire of fusible metal, a flexible insulating sheath surrounding the wire in direct contact therewith throughout and eX- tending' substantially the length thereof, and a thin flexible metallic shield surrounding the insulation from one end of the link to a point short of the other end, said shield being in electrical connection with the fuse Wire at the first mentioned end.

3. In combination in a fuse construction, comprising a fuse tube supported at one end and free at the other end with an electrical terminal adjacent the free end of the tube but spaced away therefrom to provide an air gap, a fuse wire eX- tending through the tube and connected to said terminal, means for making electrical connection between a second terminal and the end of the Wire in the tube, insulation surrounding the fuse wire, and a metallic shield surrounding the insulation on that portion of the fuse wire eX- tending through the tube and to a point outside the free end thereof, said shield having electrical connection with the end of the fuse wire lying in the tube, but not having electrical conm nection with the end lying outside the tube.

4. In combination in a fuse construction comprising a fuse tube suported at one end and free at the other end with an electrical terminal adjacent the free end of the tube but spaced away therefrom to provide an air gap, a fuse wire extending through the tube and connected to said terminal, means for making electrical connection between a second terminal and the end of the wire in the tube, insulation surrounding the fuse wire, a metallic shield surrounding the insulation on that portion of the fuse Wire extending through the tube and to a point outside the free end thereof, said shield having electrical connection with the end of the fuse wire lying in the tube, but not having electrical connection with the end lying outside the tube, and a metal member carried by the end of the tube and making contact with the shield on the fuse Wire.

5. In combination in a fuse construction, comprising a fuse tube supported at one end and free at the other end with an electrical terminal adjacent the free end of the tube but spaced away therefrom to provide an air gap, a fuse wire extending through the tube and connected to said terminal, means for making electrical connection between a second terminal and the end of the wire in the tube, insulation surrounding the fuse wire, a metallic shield surrounding the insulation on that portion of the fuse wire extending through the tube and to a point outside the free end thereof, said shield having electrical connection with the end of the fuse Wire lying in the tube, but not having electrical connection with the end lying outside the tube, and a metal member carried by the end .of the tube and having releasable spring engagement with the shield outside the fuse tube.

6. In combination in a fuse construction, comprising a fuse tube supported at one end and free at the other end with an electrical terminal adjacent the free end of the tube but spaced away therefrom to provide an air gap, a fuse wire extending through the tube and connected to said terminal, means for making electrical connection between a second terminal and the end or" the wire in the tube, and a metal member carried by the end of the tube and having releasable engagement with the wire intermediate the end of the tube and the terminal adjacent such end.

7. In combination in a fuse construction comprising a fuse tube supported at one end and free at the other end with an electrical terminal adjacent the free end of the tube but spaced away therefrom to provide an air gap, a fuse Wire extending through the tube and connected to said terminal, means for making electrical connection between a second terminal and the end of the wire in the tube and a metal member carried by the end of the tube and having an arm lying at the side oi" the tube extending out past such end and releasably engaging the fuse Wire.

LESTER C. HART. 

